A method for improving wear resistance of 3D printed 2205 duplex stainless steel

Abstract

The application provides a method for improving wear resistance of 3D printing 2205 duplex stainless steel. The application adds appropriate TiB2 particles in 2205 duplex stainless steel powder, and makes the TiB2 particles adhere to the surface of the powder particles through ball milling, and protects in argon atmosphere. In the printing process, part of the TiB2 is decomposed into TiB by the action of laser. The generated TiB and the originally existing TiB2 can act as a nucleating agent to refine the grain, and can also act as a hard point. The uniformly dispersed TiB2 reinforcement shows high adhesion and low fragmentation / breakage during sliding. At the same time, the firm interface between the TiB2 phase and the 2205 matrix prevents the peeling of particles during the wear process. The two factors work together to improve the wear resistance of 3D printing 2205 duplex stainless steel, and finally reduce the average friction coefficient from 0.7142 to 0.4305.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metal materials, and relates to a method for improving the wear resistance of 3D printing 2205 duplex stainless steel. BACKGROUND

[0002] Compared with austenitic stainless steel, 2205 duplex stainless steel is composed of ferrite (delta) and austenite (gamma), has high strength, good toughness and corrosion resistance, and is widely used in medical devices, automobile parts, ship fasteners and other fields. With the advent of a new round of scientific and technological revolution and industrial revolution, complex, miniaturization and precision have become a significant development trend. Metal 3D technology, as one of the most promising additive manufacturing technologies, is based on the principle of layered manufacturing, which uses a laser beam to melt selected areas layer by layer to realize part forming. It can be used to manufacture metal parts with complex shape, good mechanical properties, high precision and relative density close to 100%. However, due to the limitations of the properties of 2205 duplex stainless steel and metal 3D technology, the wear resistance of 3D printed 2205 duplex stainless steel parts is often poor, therefore, how to real-time control the wear resistance during SLM forming and avoid or reduce the post-processing of parts has become a major challenge in the field of metal additive manufacturing. SUMMARY

[0003] The purpose of the application is to improve the wear resistance of 3D printed 2205 duplex stainless steel to meet the requirements of 2205 duplex stainless steel in actual use.

[0004] The application provides a method for improving the wear resistance of 3D printed 2205 duplex stainless steel, which adopts two ways of overall strengthening and local strengthening. The 3D printing method adopts a doctor blade powder feeding method, and a proper amount of TiB2 particles is added to the 2205 duplex stainless steel powder before printing, and the TiB2 particles are attached to the surface of the 2205 duplex stainless steel powder by ball milling, and then printing is carried out; the powder is dried in a vacuum oven before mixing, and the temperature is controlled at 90-120 DEG C for 2-4 hours of heat preservation and 6-8 hours of drying. The addition amount of TiB2 is controlled in the range of 1% to 15% of the total mass, the particle size of TiB2 is controlled in the range of 1-5 microns, and the particle size of 2205 duplex stainless steel powder is controlled in the range of 12-53 microns. The mass ratio of ball to powder is 2:1, the total weight of the two is 6 kg, the rotation speed of ball milling is 150-250 r / min, argon is used for protection during ball milling to prevent powder oxidation, the ball milling time is 400-500 minutes, and the ball milling machine is changed in direction every half an hour and stopped for 5 minutes.

[0005] For the overall strengthening printing method, the printed part is prepared entirely using mixed powder with TiB2 strengthening particles, the printing particle size is controlled below 53 microns, argon atmosphere is used, and the process parameters are as follows: the laser power is controlled in the range of 210-290 W, the scanning speed is 600-1000 mm / s, the scanning overlap rate is 33%, the inner and outer contour scanning strategy uses multi-contour scanning, and the scanning number is 2. The internal scanning line scanning strategy uses zigzag scanning, the scanning angle is rotated by 30° on the basis of the previous layer, that is, the scanning directions of adjacent two layers are 30°, and they are alternately performed. The layer thickness is controlled at 0.03 microns. The high-precision oxygen sensor concentration is controlled to be below 800 ppm during printing, and the cavity pressure is maintained at 2.0-2.5 kPa.

[0006] For the inner and outer contour scanning strategy, multi-contour scanning is used, and the scanning number is 2, that is, the inner and outer contour scanning is increased by one scanning number on the basis of the original, so as to change the distribution of the fusing track at the boundary and improve the surface boundary performance of the part. The internal scanning line scanning strategy uses zigzag scanning, so that the directions of adjacent fusing tracks are opposite to improve the internal surface performance of the part. The scanning angle is rotated by 30° on the basis of the previous layer, that is, the scanning directions of adjacent two layers are 30°, and they are alternately performed to reduce the accumulation of thermal stress.

[0007] For the local strengthening printing method, heterogeneous powder can be used to print to achieve gradient strengthening effect, that is, the main body of the printed part is printed using 2205 duplex stainless steel powder, and the surface layer of the printed part is printed using mixed powder with TiB2 strengthening particles. The printing process parameters are the same as those of the overall strengthening. The local strengthening printing method can not only be uniformly distributed, but also can be locally strengthened in surface wear resistance, while reducing the amount of mixed powder and improving economic benefits.

[0008] For the local strengthening printing method, the neural network algorithm is used to calculate the required amount of 2205 powder for printing the main body and the required amount of 2205-TiB2 mixed powder for surface strengthening. The calculated 2205-TiB2 mixed powder is uniformly loaded at the bottom of the powder tank, and then the 2205 powder is laid on top of the mixed powder. When the 2205 powder used for printing the main body is exhausted, the printing automatically switches to using 2205-TiB2 mixed powder, realizing the local strengthening of the surface of the printed part.

[0009] The argon atmosphere is adopted to protect, and part of TiB2 is melted and decomposed into TiB by laser during printing. The generated TiB and the originally existing TiB2 can play the role of grain refinement as nucleating agent, and can also be hard points. The uniformly dispersed TiB2 reinforcement shows high adhesion, and shows low fragmentation / breakage degree during sliding. Meanwhile, the firm interface between the TiB2 phase and the 2205 matrix prevents the peeling of particles during the wear process. The two factors improve the wear resistance of the 3D printed 2205 duplex stainless steel, and finally reduce the average friction coefficient from 0.7142 to 0.4305.

[0010] Compared with the prior art, the advantages of the present application are that: (1) the ball milling process is adopted and the ball milling process parameters are controlled to enable TiB2 particles to adhere to the surface of 2205 duplex stainless steel powder, without affecting the sphericity of the powder. Thus, the two are not easy to separate during powder laying, and the uniformity of the powder laying distribution is not easy to occur; (2) TiB2 particles are adopted and an argon atmosphere is adopted to protect. TiB2 can play the role of grain refinement as nucleating agent, and can also be hard points. The uniformly dispersed TiB2 reinforcement shows high adhesion, and shows low fragmentation / breakage degree during sliding. Meanwhile, the firm interface between the TiB2 phase and the 2205 matrix prevents the peeling of particles during the wear process. The two factors improve the wear resistance of the 3D printed 2205 duplex stainless steel; (3) the inner and outer contour scanning strategy adopts multi-contour scanning, and the scanning times are 2, i.e. the inner and outer contour scanning increases the scanning times once on the basis of the original, to change the bead distribution at the boundary and improve the surface boundary performance of the part. The inner scanning line scanning strategy adopts zigzag scanning, so that the directions of adjacent beads are opposite to improve the internal surface performance of the part. The scanning angle is rotated by 30° on the basis of the previous layer, i.e. the scanning directions of adjacent two layers are 30°, which are alternately performed to reduce the accumulation of thermal stress; (4) the whole strengthening and local strengthening methods are adopted. When the whole of the printed part has high wear resistance requirements, the whole strengthening method is adopted. When the printed part only has high wear resistance requirements on the surface layer, the local strengthening method is adopted. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating laborious work.

[0012] Figure 1Process flow chart of the present application;

[0013] Figure 2 SEM images of metal powder particle size distribution, (A) TiB2 metal powder SEM; (B) 2205 duplex stainless steel powder SEM image; (C) ball-milling mixed powder SEM image;

[0014] Figure 3 Schematic diagram of internal contour line scanning strategy;

[0015] Figure 4 Schematic diagram of internal scanning line scanning strategy;

[0016] Figure 5 SEM image of 2205-TiB2 sample;

[0017] Figure 6 Comparison of wear resistance of 2205 sample and 2205-TiB2 sample;

[0018] Figure 7 Comparison of wear resistance of 2205 sample and local strengthening sample. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present application, the present application will be described in more detail and in a more complete, specific manner below in conjunction with the accompanying drawings and preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0020] Unless otherwise defined, all the professional terms used herein have the same meaning as generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present application.

[0021] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present application can be purchased from the market or can be prepared by existing methods.

[0022] In some embodiments, a method for improving the wear resistance of 3D printed 2205 duplex stainless steel according to the present application comprises the following steps:

[0023] Example 1

[0024] Step (1), mix the dried pure 2205 duplex stainless steel powder and titanium diboride powder (TiB2) in a mass ratio of 95:5 to obtain mixed powder 2205-TiB2. TiB2 as a ceramic phase can significantly improve the wear resistance. Drying removes water to avoid oxidation. Preferably, 2205 duplex stainless steel gas atomization powder with a particle size distribution of 15-53 µm (such as the powder shown in Figure 2 B) and titanium diboride powder with a particle size distribution of 1-5 µm (such as the powder shown in Figure 2The ball-to-powder mass ratio was 2:1, the total weight of the two was 6 kg, the rotation speed of the ball mill was 150 rpm, argon was used to protect the powder from oxidation during ball milling, the ball milling time was 400 minutes, and the ball mill rotation direction was changed every half hour and stopped for 5 minutes. The ball milling process parameters were controlled to enable TiB2particles to adhere to the surface of 2205 duplex stainless steel powder (as shown in Figure 2 The powder shown in the center C), while not affecting the sphericity of the powder, so that the two are not easy to separate during powder laying and the uniformity of the powder laying is not easy to occur.

[0025] Step (2), for the whole strengthening printing method, the mixed powder is used to prepare a friction and wear sample by 3D printing technology to realize the whole strengthening of the 2205 sample. The printing size is 20 mm (length) x 10 mm (width) x 10 mm (height). The 3D printing adopts selective laser melting process (SLM), the laser power is controlled within 210 W, the scanning speed is 600 mm / s, the scanning overlap rate is 33%, the internal and external contour scanning strategy adopts multi-contour scanning (as shown in Figure 3 The scanning number is 2, the internal scanning line scanning strategy adopts zigzag scanning, the scanning angle is rotated by 30° on the basis of the previous layer, that is, the scanning directions of the adjacent two layers are 30° (as shown in Figure 4 The scanning directions of the adjacent two layers are 30° (as shown in Figure 6 The scanning directions of the adjacent two layers are 30° (as shown in

[0026] Example Two

[0027] Step (1), the dried pure 2205 duplex stainless steel powder and titanium diboride powder (TiB2) are mixed in a mass ratio of 95:5 to obtain a mixed powder 2205-TiB2. TiB2 as a ceramic phase can significantly improve the wear resistance. Drying removes moisture to avoid oxidation. Preferably, the 2205 duplex stainless steel gas-atomized powder has a particle size distribution of 15-53 pm, and the titanium diboride powder has a particle size distribution of 1-5 pm. The ball-to-material mass ratio is 2:1, the total weight of the two is 2 kg, the ball milling speed is 150 rpm, argon is used for protection during ball milling to prevent powder oxidation, the ball milling time is 400 minutes, and the ball milling direction is changed every half hour and stopped for 5 minutes. Control the ball milling process parameters so that the TiB2 particles can adhere to the surface of the 2205 duplex stainless steel powder, while not affecting the sphericity of the powder, so that the two are not easily separated during powder laying and the uniformity of the powder distribution is not easily caused by uneven mixing of the powder.

[0028] Step (2), for the printing method of local strengthening, the neural network algorithm is used to calculate the required 2205 powder for printing the main body as 2.3 kg and the required 2205-TiB2 mixed powder for surface strengthening as 0.2 kg. The calculated 2205-TiB2 mixed powder is evenly loaded into the bottom of the powder tank, and then the 2205 powder is laid on top of the mixed powder. When the 2205 powder used for printing the main body is exhausted, it automatically switches to using 2205-TiB2 mixed powder for printing, achieving local strengthening of the surface wear resistance and reducing the amount of mixed powder to improve economic benefits. The powder is used to prepare a friction and wear sample by 3D printing technology to realize local strengthening of the 2205 sample. The printing size is 20 mm (length) x 10 mm (width) x 10 mm (height). The 3D printing adopts the selective laser melting process (SLM), the laser power is controlled within 210 W, the scanning speed is 600 mm / s, the scanning overlap rate is 33%, the inner and outer contour scanning strategy adopts multi-contour scanning, the scanning times are 2, the internal scanning line scanning strategy adopts zigzag scanning, the scanning angle is rotated by 30° based on the previous layer, that is, the scanning directions of adjacent two layers are 30°, and they are alternately performed. The layer thickness is controlled at 0.03 microns. The concentration of the high-precision oxygen sensor is maintained below 800 ppm during printing, and the cavity pressure is maintained at 2.0-2.5 kPa. After printing, the sample is taken for friction and wear performance test. By comparing the friction coefficient curves of the locally strengthened sample and the 2205 sample, the friction coefficient of the locally strengthened sample is significantly reduced, and the wear resistance is significantly improved (as shown in Figure 7 ).

[0029] The above is only the preferred embodiment of the present application, and does not limit the present application in any form. Therefore, any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application, without departing from the technical scheme of the present application, shall fall within the protection scope of the technical scheme of the present application.

Claims

1. A method for improving the wear resistance of 3D-printed 2205 duplex stainless steel, characterized in that, Two methods, overall strengthening and local strengthening, are employed. The 3D printing method uses a scraper-feed powder method. Before printing, an appropriate amount of TiB2 particles are added to the 2205 duplex stainless steel powder, and ball milling is used to adhere them to the surface of the 2205 duplex stainless steel powder before printing. Before mixing the powder, it needs to be vacuum dried in a vacuum chamber at a temperature controlled at 90-120℃ for 2-4 hours and then dried for 6-8 hours. The amount of TiB2 added is controlled within the range of 1% to 15% of the total mass, the particle size of TiB2 is controlled at 1-5 micrometers, and the particle size of the 2205 duplex stainless steel powder is controlled at 12-53 micrometers. The ball-to-powder mass ratio is 2:1, the ball mill speed is 150-250 rpm, and argon gas is used for protection during ball milling to prevent powder oxidation. The ball milling time is 400-500 minutes. After every half hour of ball milling and powder mixing, the ball mill direction is changed and stopped for 5 minutes. For the overall strengthening printing method, all printed parts are prepared using a mixed powder with added TiB2 strengthening particles. The printing particle size is controlled below 53 micrometers, and an argon atmosphere is used. The process parameters are as follows: laser power is controlled within the range of 210-290W, scanning speed is 600-1000mm / s, scanning overlap rate is 33%, and the inner and outer contour scanning strategy adopts multi-contour scanning with 2 scans. The internal scanning line scanning strategy adopts zigzag scanning, with the scanning angle rotated by 30° based on the previous layer, that is, the scanning direction of adjacent two layers is 30°, alternating, and the layer thickness is controlled at 0.03 micrometers. During printing, the concentration of high-precision oxygen sensor is maintained below 800ppm, and the internal gas pressure is maintained at 2.0-2.5kPa. The inner and outer contour scanning strategy employs multi-contour scanning with two scans, meaning that the inner and outer contour scanning adds one more scan to the inner circle to change the melt channel distribution at the boundary and improve the surface boundary performance of the part; the internal scan line scanning strategy employs zigzag scanning, making the directions of adjacent melt channels opposite to improve the internal surface performance of the part; the scanning angle is rotated by 30° from the previous layer, meaning that the scanning directions of adjacent two layers are 30° apart, and are performed alternately to reduce thermal stress accumulation; For localized strengthening printing, heterogeneous powder printing is used to achieve a gradient strengthening effect. That is, the main body of the printed part is printed with 2205 duplex stainless steel powder, and the surface of the printed part is printed with mixed powder with added TiB2 strengthening particles. The printing process parameters are the same as those for overall strengthening.

2. The method for improving the wear resistance of 3D-printed 2205 duplex stainless steel as described in claim 1, characterized in that, For the localized strengthening printing method, a neural network algorithm is used to calculate the amount of 2205 powder required for printing the main body and the amount of 2205-TiB2 mixed powder required for surface strengthening. The calculated 2205-TiB2 mixed powder is evenly loaded into the bottom of the powder cylinder, and then 2205 powder is spread on top of the mixed powder. As printing progresses, when the 2205 powder used for printing the main body is exhausted, the printing automatically switches to using 2205-TiB2 mixed powder to achieve localized surface strengthening of the printed part.

3. The method for improving the wear resistance of 3D-printed 2205 duplex stainless steel as described in claim 1, characterized in that, Using an argon atmosphere for protection, some TiB2 reacts with the laser during the printing process and melts and decomposes into TiB. The generated TiB and the original TiB2 act as nucleating agents to refine the grains and as hard particles. The uniformly dispersed TiB2 reinforcement exhibits high adhesion and low fragmentation / fracture during sliding. At the same time, the strong interface between the TiB2 phase and the 2205 matrix prevents the particles from peeling off during wear, ultimately reducing the average friction coefficient from 0.7142 to 0.4305.

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